The invention relates to a device for crimping synthetic thread bundles or strips.
A device that already has the characteristics of this preamble is known from British Patent 487 711. In this device, the two rollers that can be driven in contrary directions are disposed--as is usual in compression crimping devices--above one another. The upper roller is provided with edge disks. The compression chamber has a fixed bottom plate, which is disposed parallel to and a short distance from the plane of the roller gap, and a pivotable top plate. The opening of the orifice of the compression chamber is located at the level of the plane of the roller gap. The compression chamber extends approximately as far as the edge of the edge disks, whose diameter is approximately 1.5 times the roller diameter and cannot be selected substantially larger, for geometric reasons. The compression chamber is therefore comparatively small, compared with the diameter of the rollers.
German Patent Disclosure DE-OS 21 15 688 describes a device in which again one of the two rollers is provided with edge disks. In this device, the compression chamber is substantially larger, compared to the dimensions of the rollers. However, the inner faces of the edge disks form the lateral boundary faces only in a small region in the surroundings of the roller gap. By far the greater portion of the side faces is covered by fixed walls. There is necessarily a seam between the edge disks, which rotate with the rollers, and the fixed walls
The same is true for another device, which is described in German Patent Disclosure DE-OS 20 21 103.
From German Patent Disclosure DE-OS 35 03 447, a device is known which is distinguished from the last two devices explained above in particular that the two rollers each have one edge disk, and the two edge disks are mounted on opposed face ends.
The subject of German Patent Disclosure DE-OS 38 36 646 is a compression crimping device, in which one roller is disposed in the interior of another roller, the latter embodied as an annular roller. There is a roller gap between the jacket face of the inner roller and the inside face of the annular roller.
One of the two rollers, which can be driven in the same direction, is provided with edge disks, which embrace the other roller. The edge disks, over the entire length of the compression chamber, form two opposed lateral boundary faces. Other boundary faces are formed by the inside face of the annular roller and by the jacket face of the inner roller. The compression chamber is therefore like the pointed end of a crescent, in side view. Because of the curved form, there is necessarily--in a deviation from all the other devices explained above--a spacing between the orifice opening and the plane of the roller gap. By the provision of a roller in the interior of an annular roller, the geometric conditions are made quite complicated and are greatly restricted. The compression chamber itself is therefore--compared with the dimensions of the overall device--rather small. Problems arise, particularly with respect to delivering the thread bundle to be compressed to the roller gap and drawing off the crimped material.
In many modern crimping devices, as can be learned from European Patent Disclosure EP 0 256 257 A2, for instance, a rotating pressure disk is let into a fixed side plate of the compression chamber and seals off the especially critical surroundings of the roller gap. Between the pressure disk and the side plate, there is intrinsically a seam. Compression chambers of this or similar design generally process yarn cables of very high titer of up to a few million dtex, at low speeds of up to about 300 or at the most 400 m/min.
The invention takes as its departure the problems presented particularly in crimping machines that run at substantially higher speeds. One such crimping machine is described for instance in German Patent Disclosure DE-OS 33 32 387. The compression chamber of rectangular cross section is enclosed by smooth boundary walls which are immovable in operation. Although speeds of 2000 m/min are mentioned in this reference, nevertheless in actual use this machine usually runs at speeds of up to about 1000 m/min and handles titers in the range of approximately 10,000 to 100,000 dtex. In operation, friction between the wall faces and the thread plug found in the compression chamber creates heat, so that at high speed the threads can even melt. There are accordingly limits to increasing the operating speed. At high speeds, increasing problems also arise from the fact that the thread catches at the gaps between the rotating roller and the stationary wall faces.
The inventors have recognized that the combination of characteristics recited in the preamble and known from British Patent 487711 offers the possibility, in high-speed crimping, of reducing the heating caused by friction considerably and reducing the danger that the threads will catch. Each face element of the inside faces of the edge disks is in contact with the thread plug for only a relatively brief period of time per revolution and thus is heated hardly at all. During the brief phase of contact, the relative speed between the plug and the inside faces of the edge disks is markedly lower than in compression chambers with fixed wall faces. The side wall faces are free of seams, so the thread is prevented from catching, at least in those regions.